On average, how many gallons of water falls per square foot of roof area from a 1" rainfall event?

When considering rainfall, it's essential to understand how much water accumulates on a roof area during a precipitation event. A 1-inch rainfall means that for every square foot of area, there will be a volume of water that is equal to the rainfall depth.

To break it down: 1 inch of rain corresponds to a specific volume over a square foot of surface area. There are 12 inches in a foot, so if we think about it in terms of cubic inches, 1 inch of water over a square foot is equivalent to:

1 square foot × 1 inch = 1 square foot × (1/12) feet = 1/12 cubic feet.

To convert cubic feet to gallons, it's useful to know that there are approximately 7.48 gallons in a cubic foot.

Thus, calculating the volume of water from a 1-inch rainfall over a square foot of area gives us the following:

(1/12) cubic feet × 7.48 gallons/cubic foot ≈ 0.62 gallons.

This indicates that for every square foot of roof area, approximately 0.62 gallons of water will fall during a 1-inch rainfall event. This figure aligns with the physics of water accumulation and emphasizes the